sqlalchemy.exc.CircularDependencyError

Raised by topological sorts when a circular dependency is detected.

There are two scenarios where this error occurs:

• In a Session flush operation, if two objects are mutually dependent on each other, they can not be inserted or deleted via INSERT or DELETE statements alone; an UPDATE will be needed to post-associate or pre-deassociate one of the foreign key constrained values. The post_update flag described at :ref:`post_update` can resolve this cycle.
• In a _schema.MetaData.sorted_tables operation, two _schema.ForeignKey or _schema.ForeignKeyConstraint objects mutually refer to each other. Apply the use_alter=True flag to one or both, see :ref:`use_alter`.